For the 20 different comparisons, we included three mutant-allele expressing clones (T158M, 803delG, R168X) and four completely skewed wild-type MeCP2 expressing LCLs (R106W, R255X, 803delG, 803delG) from different donors.

Clonal cell lines with the mutant MECP2 allele on the active X chromosome were derived from lymphoblastoid cell lines (LCLs) from four females with clinically diagnosed Rett syndrome and known mutations (T158M, 803delG, R168X) [ 10 ] and 1159del28 (unpublished) using the technique described above.

Four cell lines from females with known MECP2 mutations (R106W, R255X, and two with 803delG) but completely skewed X chromosome inactivation with the wild-type MECP2 allele on the active X chromosome were also cultured.